[TheFattestNinja]

I mean you had your share of tough love already in this thread. But: - The examples you posted are indeed very simple problems. Caesar is just about "can you scan two arrays at the same time" (and then do charString + charKey and some modulo). Luhn is just a step of non-obvious specification to follow.

- This is a different game than your day to day. Those two being easy stuff means nothing if you never played the game.

- Now you moved a "unknown unknown" to the category of "known unknowns". You know you have no competence in this category, and if you wish to improve in it you can do so. Or not, it's your choice. Before, you didn't have the choice. So that's good!

- It's not about the language. You can solve these in Java, C, Assembly, Haskell. Most training website for interview questions (like these) allow you to implement in any of the major languages. If you want to play the game and get better, I recommend Hackerrank (for structure) and TopcoderArena (for variety, since they give you a bit more fuzzy spec and you also need to identify the algo for the issue at hand). The latter is slow as balls though, and offers no solution (except the best submitted, which may be cryptic).

- This stuff takes time, and if you want to learn about things you'll have to book up. Cormen's "Intro to algorithms" or Skiena's Manual are the goto texts. They are thick. Take your time. Persevere.